The major goals of this project are to characterize the host's immune response to helminth infections and to relate the findings to the pathogenesis of clinical disease. In filariasis the heterogeneity of disease expression may relate to variable patterns in immune recognition and response or to pre-natal exposure to parasite antigen. Immunochemical analysis of serum from patients & neonates to detect the relevant immunogens and allergens of the parasite are under way. The role of immune complexes in the pathogenesis of filariasis and schistosomiasis is also being explored. Immunologic hyporesponsiveness to parasitic antigens is characteristic of chronic helminth infections. Humoral and cellular suppressive mechanisms which regulate the lymphocyte responsiveness in human schistosomiasis are being defined as are changes in responsiveness following treatment of the infection. Immediate hypersensitivity (IgE) responses have been found to be modulated by IgG blocking antibodies which develop in human filariasis and schistosomiasis. Eosinophils are prominent in the host response to helminth infections. Purification of these cells has been achieved with the flourescence activated cell sorter.